Frieghtliner century class running light not working

Did someone replace any of the air switches inside you're dash manifold located right behind ashtray on you're firewall someone mixed the wiring for this manifold big time that's all you're psi switches for brakes cruise lights air gauge alarms and everything

 

so now u have it to take it back and tell them to do the job properly I have an old diagram from frightliner but u need to open up dash and chase down all the wire numbers its tough to get it back to normal again but where ever u had it done take it back and they have to fix it nothing u can do about it or got to freight liner and send them the bill

 

You've got a short somewhere. When you turn your headlights on there's a wire grounding out. Check your pigtail. Remove it completely then see if it does it. If it does then it's truck side. If not then it's trailer side.

 

nasriza is correct.it is a problem with the wiring that goes to the switches on the air manifold.the wiring was wrong and now a switch has failed.get a diagram and wire correctly.good luck.

 

U can go by a freight liner dealer they should be able to print one for u it shouldn't be that hard